Pheromones (chemicals released by an organism that cause behavioral or physiological responses among other members of the same species) appear to play an important role in the behavior of zooparasitic nematodes. These compounds may be essential for communication between the sexes prior to mating and, based on Nippostrongylus brasiliensis as a model system, may also govern certain processing of helminth population dynamics. This proposal seeks to continue various chemical and biological investigations of the involvement of pheromones in the Nippostrongylus model. Particular emphasis will be placed on the elucidation of the physiological and environmental factors that influence the pheromone communication system. Chemical studies will be directed toward the further stabilization and purification of one apparent compound(s) for eventual identification. Other biologically active compounds that exhibit pheromonal properties will be studied through initial purification and stabilization steps. More exploratory studies will approach the involvement of primer pheromones in regulating various developmental and/or physiological processes in the Nippostrongylus model. Throughout the course of experimentation, the developing data base will be assessed from the perspective of designing feasibility studies that employ pheromones as highly selective, safe pharmaceutical agents for control of helminthic diseases.